then discuss the future directions that will be taken as a direct result of the work

accomplished in this dissertation.

Chapter 2: Integration of Unequal Length b Subunits into F1Fo ATP Synthase

 The work presented in Chapter 2 stemmed from observations made by Dr. Paul

Sorgen in our laboratory that b subunits with deletions of up to eleven amino acids and

insertions of up to fourteen amino acids, corresponding to approximately 16 A+ and 21 A+,

respectively, formed intact and functional F,Fo ATP synthase complexes (193, 194).

This work had suggested that the tether region of the b subunit possesses a certain degree

of flexibility. However, it was not known whether this flexibility extended to the

dimerization of two b subunits of unequal lengths and their incorporation into an enzyme

complex. An experimental system was developed to allow expression of two different b

subunit genes and determine whether the differing b subunits were assembled into an

F1Fo ATP synthase complex. The experiments involved an epitope tag system that

allowed us to determine if the different b subunits segregated into homodimers, or

alternatively, if a heterodimer of long and short b subunits can be incorporated into an

F1Fo ATP synthase complex. The histidine and V5 epitope tags introduced into the b

subunits did not appreciably affect enzyme assembly or function. Expression of two

different wild-type length b subunits led to three distinct F1Fo ATP synthase complexes in

the same cell; 1) a homodimer of histidine-tagged b subunits, 2) a homodimer of V5-

tagged b subunits and 3) a heterodimer consisting of a histidine-tagged b and a V5-tagged

b subunit.

 More importantly, three different F1Fo ATP synthase complexes were present

even when the b subunits were not of identical length. We observed dimerization of b